Volume 9, Number 1 Bioenergy 

Edition

A Chip 

Off the 

Old Block

page 5 Chip and Truck

page 26

Which Do 

You A-door?

page 13

How Now

Round Crown?

page 37
With thanks to:

Julie Schreck

Bitterroot National Forest

Forest Service

Project Learning Tree

http://www.plt.org

Natural Inquirer

Produced by

Forest Service

Cradle of Forestry Interpretive 

Association

Production Staff

Babs McDonald, Forest Service

Rachel Small, Cradle of 

Forestry Interpretive 

Association

Jessica Nickelsen, Cradle 

of Forestry Interpretive 

Association

Michelle Andrews, University 

of Georgia

Vicki Arthur, Forest Service

Forest Service

Gail Kimbell, Chief

Ann Bartuska, Deputy Chief, 

Research and Development

John Sebelius, Staff Director, 

Science Quality Services

Jim Hubbard, Deputy Chief, 

State and Private Forestry

Safiya Samman, Staff Director, 

Conservation Education

Marcia Patton-Mallory, Woody 

Biomass and Bioenergy 

Coordinator

Cradle of Forestry 

Interpretive Association

Alex Comfort, Executive 

Director

Bill Alexander, Chairman

Bioenergy Edition • Volume 9, Number 1 • Spring 2009

Participating Scientists

Forest Service

David Calkin, Rocky Mountain 

Research Station

J. Greg Jones, Rocky Mountain 

Research Station

Timothy Maker, Forest 

Products Laboratory

Robert Ross, Forest Products 

Laboratory

D. Andrew Scott, Southern 

Research Station

Janet Stockhausen, 

Washington Office

Collaborating Scientists

Richard Bergman, Eastern 

Research Group

Thomas Dean, Louisiana State 

University

Melissa Huff, Franklin 

Associates

Dan Loeffler, University of 

Montana

Robin Silverstein,

Management and 

Engineering Technologies, 

Inc.

Martin Twer, University of 

Montana

Hans Zuuring, University of 

Montana
1

The Natural Inquirer • Volume 9, Number 1

What’s Inside

Editorial Review Board . . . . . . . . . . . . . . . . . . . . . . . . . 2

About the Natural Inquirer . . . . . . . . . . . . . . . . . . . . . . 3

Who Are Scientists? . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Welcome to the Bioenergy Edition of the Natural 

Inquirer! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Note to Educators . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Lesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Contents

A Chip Off the Old 

Block

Using Wood Chips To Heat School Buildings

Which Do You A-door?

Comparing the Energy Used To Make Wood 

and Steel Doors

Chip and Truck

Comparing the Costs and Benefits of Using 

Trees for Heat

How Now

Round Crown?

Predicting the Future Energy Benefits

of Tree Crowns

Reflection Section Answer Guide . . . . . . . . . . . . . . 52

Which National Science Education Standards Can Be 

Addressed By These Articles? . . . . . . . . . . . . . . . 56

What Is the Forest Service? . . . . . . Inside back cover

What Is the Cradle of Forestry Interpretive

Association? . . . . . . . . . . . . . . . . . Inside back cover

Editorial Review Board . . . . . . . . . . . . . . . . Back Cover

Additional Web Resources . . . . . . . . . . . . . Back Cover

5 13

26 37
2

Bioenergy Edition, http://www.naturalinquirer.org

Editorial Review Boards 

Natural Inquirer review boards.

Michelle Rabold’s 7th grade classes, Clarke Middle School, Athens, Georgia

Natural Inquirer editorial review boards hard at work.

The Natural Inquirer is reproduced on recycled paper with soy-based inks. Please pass this journal along or recycle it when you have finished using it. 

http://www.naturalinquirer.org

“Thanks for the help to learn new words.”

“It helped me to learn something new.”

“I like the bees.”

“The glossary should say which page

each word appears on.”

“Thinking About Science: Good ending—

makes us think.”

“I like how you put a glossary for words people might 

not know.”

“Good work, I enjoyed looking at this.”

“The pictures help out a lot.”

Comments from the National Inquirer editorial review boards:
3

The Natural Inquirer • Volume 9, Number 1

About the Natural Inquirer

Who Are Scientists?

Scientists are people who collect and 

evaluate information about a wide range 

of topics. Some scientists study the 

natural environment. To be a successful 

environmental scientist, you must:

b Be curious—You must be interested in 

learning.

b Be enthusiastic—You must be interested 

in an environmental topic.

Scientists report their research in 

journals, which are special booklets that 

enable scientists to share information 

with one another. This journal, the Natural 

Inquirer, was created so that scientists can 

share their research with you and with other 

middle school students. Each article tells you 

about scientific research conducted by scientists 

in the Forest Service, U.S. Department of 

Agriculture. If you want to know more about 

the Forest Service, you can read about it on the 

inside back cover of this journal, or you can visit 

the Natural Inquirer Web site at http://www.

naturalinquirer.org.

All of the research in the Natural Inquirer is 

concerned with nature, such as trees, forests, 

animals, insects, outdoor activities, and 

water. First, you will “meet the scientist” who 

conducted the research. Then you will read 

something special about science and about the 

natural environment. You will also read about a 

specific research project. This is written in the 

format that scientists use when they publish 

their research in journals. Then, YOU will 

become the scientist when you conduct the 

FACTivity associated with each article. Don’t 

forget to look at the glossary and the special 

sections highlighted in each article. These 

sections give you extra information.

At the end of each section of the article, you 

will find a few questions to help you think about 

what you have read. They should help you to 

think more about the research. Your teacher 

may use these questions in a class discussion.

b Be careful—You must be accurate in 

everything that you do.

b Be open minded—You must be willing to 

listen to new ideas.

b Question everything—You must think 

about what you read and observe.
4

Bioenergy Edition, http://www.naturalinquirer.org

Welcome

to the Bioenergy Edition of the Natural Inquirer!

What is energy? It is the ability to 

do work and the ability of certain 

forces in nature to do work. It is 

also thought of as the resources humans use to 

produce power, such as coal, oil, wood, wind, 

and gas. Everything living needs energy to 

grow, reproduce, and survive.

People use energy to do even more than 

grow, reproduce, and survive. People use 

physical energy to mechanically move 

from place to place; to heat, cool, and light 

buildings; to wash clothes; and to operate 

TVs and computers. As energy needs 

increase and our regular sources of energy 

become less available, society is more 

concerned with finding new sources of 

energy.

This edition of the Natural Inquirer is 

concerned with a new source of energy. The 

source of energy explored in this Natural 

Inquirer is really an old source. This type 

of energy was used before humans began 

using coal, oil, and gas. Can you guess what 

that energy source is? If you guessed wood, 

you are right! But it is actually more than 

just wood, because it can include a wide 

variety of plant material. Scientists now call 

this source of energy biomass, biofuel, or 

bioenergy.

What is bioenergy? The living (or onceliving) material in an area is known as 

biomass. Bio means life. (Think of biology, 

the study of life.) Biomass can also refer to 

plant materials and animal wastes used as 

a source of fuel. In this case it is known as 

biofuel or bioenergy. In this edition of the 

Natural Inquirer, we’ll explore ways that 

bioenergy contributes to our energy future.

Bioenergy is studied by scientists in a 

number of scientific areas. These areas 

include, for example, wood science; climate 

change; the development and care of forests 

(or silviculture [sil vuh kul chür]); and the 

production, distribution, and use of goods and 

services (or economics). Biomass studies help 

scientists understand how forest products 

can help address current and future energy 

questions. For example, bioenergy studies may 

look at the use of bioenergy for food, building 

materials, fuel, clothing, and paper.

How do you think the use of bioenergy 

for building materials can help address energy 

concerns? You will find out in this edition of 

the Natural Inquirer! Can bioenergy help a 

school save money so it can spend more on 

books and computers? You will see! You will 

also learn whether trees may be a future 

source of energy, and which trees might be 

best to heat your home or fuel your car.

Scientists believe we can replace 30 

percent of our oil-based fuel with bioenergy. 

Of this bioenergy, 27 percent could come 

from forests, and 73 percent could come from 

agriculture. The use of bioenergy to address 

energy concerns has one very big advantage. 

Trees and crops are renewable! In contrast 

with oil, trees and crops can be planted, 

cared for, cut and used, and planted, again. 

The main sources of energy we use now, 

such as oil, coal, and gas, are not considered 

renewable because it would take hundreds or 

thousands of years to replenish their supply.

As you read the articles in this Natural 

Inquirer, think about the many ways forests 

can help address our energy future.

Educators: Review “Note to Educators” 

on page 47 before using this Natural Inquirer. 

http://www.naturalinquirer.org
5

The Natural Inquirer • Volume 9, Number 1

A Chip 

Off the 

Old Block

Using Wood 

Energy To 

Heat Schools

5

The Natural Inquirer • Volume 9, Number 1
6

Bioenergy Edition, http://www.naturalinquirer.org

Meet the Scientists

Dr. Rick Bergman, Chemical Engineer: 

My favorite science experience was working 

with two communities in southern Mexico.

The communities were hoping to use more 

of their natural resources to become more 

self-sustaining as a community. I was able to 

give them concrete ideas on how to dry wood 

that was cut from local trees. This allowed 

community members to manufacture wood 

furniture to sell to local schools. I was grateful 

to be a part of the team assisting other people 

who want a better life for themselves and their 

communities. t

s

Dr. Tim Maker, Wood Energy Scientist: I 

studied engineering and physics in college. My 

memorable experience was when a professor 

explained to all of us in his physics class about 

what he did as a scientist. He had to know a lot 

about computers, electronics, and work very 

hard.

Glossary

a as in ape

ä as in car

e as in me

i as in ice

o as in go

ô as in for

u as in use

ü as in fur

oo as in tool

ng as in sing

Pronunciation Guide

Accented syllables are in bold.

natural resources (na cha rôl re sôrs es): 

Supplies of things in nature that take care of a 

human need, such as oil, wood, or water.

sustaining (suh stan ing): Keeping up or 

maintaining.

nutrients (noo tre ents): Any of the substances 

found in food that are needed for the life and 

growth of plants and animals.

forest managers (för est mä ni jürs): Skilled 

individuals who take care of natural resources.

biomass (bi o mas): All the living or once-living 

things in a particular area.

operational (op ür a shun ul): Of or relating to 

performance of practical work or operations.

renewable natural resource (re nu uh bool 

na cha rôl re sôrs): An environmental source 

of supply or support that can be renewed by 

ecological processes or management practices.

average (av rij): The usual kind or amount.

The number gotten by dividing the sum of two 

or more quantities by the number of quantities 

added.

conventional (kän ven chun ul): Ordinary.
7

The Natural Inquirer • Volume 9, Number 1

Thinking About Science

Research always has a purpose behind it. Is the research being done just to learn 

something new? Is its purpose to solve a problem? When scientists study a question 

to satisfy their curiosity about something, the research is called basic science. An 

example of basic science is when astronomers study the planet Mars. This kind 

of research is important, as it touches the mysteries of life. Often, basic science 

provides new information that can be used in the future to help solve problems. Most 

research being done today is done to solve problems. This kind of research is called applied science. 

Medical research is applied science, and most natural resource and environmental science is applied 

science. In the research you will read about in this article, the scientists hoped to solve a problem 

and help schools save money. Would you call this research basic or applied science?

Figure 1. Location of Darby, Montana.

Montana N. Dakota

S. Dakota

Wyoming

Idaho

=Darby, Montana

http://www.50states.com

N

Introduction

As you read in “Thinking About the 

Environment,” forest managers were looking 

for a way to use small trees that were being 

cut from the forests. One of the historic uses 

of wood was for heating. In recent years, 

however, most heating in the United States has 

come from other sources of energy, such as 

petroleum, gas, and electricity. The scientists in 

this study wondered if using wood for heating 

would save schools money compared to the 

way the schools are usually heated. The school 

district in Darby, Montana, was interested in 

the same question (figures 1 and 2). 

Thinking 

About the 

Environment

You may have heard about 

the wildfires that sometimes 

burn in the Nation’s forests. In 

some cases, wildfires now burn hotter, longer, 

and over a wider area than wildfires of the past. 

This is because many forests today contain a 

lot of fuel. This fuel is often made up of many 

small-sized trees, which are growing because 

forest fires have not been allowed to burn 

there in the past. Before human development 

occurred in and near forests, wildfires could 

burn and, when they burned, they burned the 

small trees and other vegetation near the forest 

floor. Now that development occurs near and 

in the forests, we have not allowed wildfires to 

burn. The result is a lot of fuel in the form of 

small trees. One way to address this problem is 

to cut the small trees.

Cutting trees is expensive. To many people, 

it makes more sense to have a use for any tree 

that has been cut. To other people, leaving the 

small trees to decay in the forest also makes 

sense. This is because a decaying tree returns 

nutrients to the forest soil. This article describes 

how schools used these trees to help them heat 

their buildings. In this research, the small trees 

were used in a wood heating system built just 

for the school. Do you think this is a good use 

for the small trees? Why or why not?
8

Bioenergy Edition, http://www.naturalinquirer.org

Reflection Section

b	 Whatis the question the scientistswanted to

answer?

b Whatwould the scientists have to do to

answertheir question?

Method

The scientists worked with partners to build 

the wood heating system. Such a system uses 

biomass heat energy. The new heating system 

included the following parts:

1. Boiler house: A central building that houses 

the wood-burning boiler and a large wood 

storage bin (figure 3).

2. Wood heating system: Includes the boiler, 

the storage bin, and automated belts to carry 

the wood from the storage bin to the boiler 

(figure 4).

3. Heat distribution system: A series of 

underground pipes to carry the heat to the 

three schools. This system used existing 

pipes but improved them as needed.

4. Improvements to existing heating equipment: 

Wherever possible, existing equipment was 

used for the new system. Also, the existing 

oil heating system was improved so it could 

be used as a backup to the new wood 

heating system.

The scientists kept careful records of all costs 

to build and operate the new heating system. 

They tracked operational costs for 2 school 

years.

Figure 3. The Darby school’s wood-burning 

boiler.

Figure 4. The Darby wood heating system. Note 

the wood is cut into wood chips and carried on a 

moving belt before it is stored in the storage bin.

Figure 2. Darby Junior High School
9

The Natural Inquirer • Volume 9, Number 1

Reflection Section

b	 Should the scientists include the following costs in their calculations: The cost of cutting trees,the

cost oftransporting cuttrees to amillfor cutting into chips, and the cost oftransporting thewood

chips to the school?Why orwhy not?

b	 Biomass heat,which comes fromwood chips, is considered a renewable natural resource because

trees can be replanted.Whatis one advantage of using biomass energy over a nonrenewable

resource such as oil?Whatis one disadvantage?

Findings

The scientists compared the costs of the new biomass heating system with average historical 

costs of heating with oil and gas (table 1). Previously, oil had been used to heat the schools, and 

liquid propane (LP) gas was used to produce hot water. The new biomass heat system heated both 

the schools and the water, eliminating the need for LP gas. 

Table 1. Comparison of historic costs for heating and the new biomass energy system. Note that in 

2004–2005, historical usage costs included an estimate for the rising cost of oil.

------Average Historical Usage----------- --------------------2003–2004 School Year -------------

OIL COST 

($)

COST OF 

LP GAS ($)

TOTAL 

COST OF 

OIL/LP GAS 

($)

OIL COST 

($)

WOOD 

COST ($)

TOTAL 

COST OF 

WOOD/OIL

SAVINGS 

($)

51,884 2,080 53,964 11,080 18,357 29,437 24,527

------Average Historical Usage----------- --------------------2004–2005 School Year -------------

OIL COST 

($)

COST OF 

LP GAS ($)

TOTAL 

COST OF 

OIL/LP GAS 

($)

OIL COST 

($)

WOOD 

COST ($)

TOTAL 

COST OF 

WOOD/OIL

SAVINGS 

($)

88,060 2,500 90,560 2,451 26,660 29,051 61,509
10

Bioenergy Edition, http://www.naturalinquirer.org

Number Crunches

b	 Estimate the percentage ofthe cost savings

for both school years. You can do this by

rounding the average total historic cost and

the total yearly costfor both years. Round

each to the nearest1,000.For each year,

divide the yearly cost by the average total

historic cost, and subtractthat number

from100. Thiswill give you an estimate of

the percentage cost savings for each year.

Did the percentage of cost savings increase

or decrease between the 2003–2004 and

2004–2005 school years? By howmuch?

Reflection Section

b	 Look attable 1. You can see the cost of

oil had risen between 2003 and 2005, and,

therefore,the cost savings rose overthe 2

years. Based onwhat you knowabout oil

prices now, do you think the cost savings

forDarby schoolswent up, down, or stayed

the same during the last school year as

comparedwith 2004–2005?

b Do you think the cost savingswould be the

same for a school located in Kansas as in

Montana?Why orwhy not?

Discussion

By using biomass wood energy for heating, 

the Darby School District saved almost 50 

percent of its fuel costs in 2003–2004, and 

almost 70 percent in 2004–2005. These costs 

do not include the cost of building the new 

biomass energy system and improving the old 

heating system. For a moment, let’s include 

those costs, which were a little less than 

$1,000,000. The scientists concluded that over 

a 20-year period of saving energy costs, the 

biomass heat energy system would pay for itself. 

This is largely due to the increasing costs of oil 

compared with the cost of wood chips.

It is costly to convert a conventional heating 

system into a biomass energy system, as was 

done in Darby. The scientists suggest the best 

time to install a biomass heating system is when 

new schools are being built. If new schools 

are close to a local source of wood chips, they 

should save a lot of money in energy costs.

Reflection Section

b	 Should the cost ofreplacing a conventional

heating systemwith a newbiomass system

be consideredwhen calculating cost

savings?Why orwhy not?

b Should the cost of building a newbiomass

heating systemat a newschool be

consideredwhen calculating cost savings?

Why orwhy not?

Adapted from Bergman, R. and Maker, T. M. 2007. Fuels for schools: Case study in Darby, Montana, Forest Service 

General Technical Report FPL-GTR-173. Madison, WI: Forest Service, Forest Products Lab. 21 pp. http://www.fpl.fs.fed.

us/documnts/fplgtr/fpl_gtr173.pdf.
11

The Natural Inquirer • Volume 9, Number 1

FACTivity

Time Needed

5 minutes at the end of a previous class 

period

1 class period

In this FACTivity, you will consider the 

source and availability of different types 

of energy for heating your school. The 

questions you will answer in this activity 

are:

1. What is the most reliable source of 

energy for our school right now?

2. What might be the most reliable 

source of energy for our school in 10 

years?

Method

At the end of a previous class period, 

take approximately 3 minutes to do the 

following activity.

In a rapid brainstorming session with the 

entire class, list as many types and sources 

of energy as you can. Examples include 

U.S. offshore oil, oil imported from other 

countries, local wind power, electricity 

from water sources (turbines at dams), 

geothermal energy, electricity from nuclear 

power, etc. You may want to start by listing 

the types of power (such as electricity), 

then the sources for each (such as nuclear, 

water, etc.).

In the next 2 minutes, class members 

should organize into groups of four 

students, based on a type of energy 

identified. For example, one group might be 

the windpower group. Another group might 

be the biomass energy group.

For homework, research the sources 

and availability of your energy type. Take 

windpower, for example. Where are the 

best locations to place windmills? To 

use energy from windmills, what is the 

maximum distance a school can be located 

from the windmills? Write up one-half page 

to turn in for the assessment.

When you have had enough time to do 

your independent research, your teacher 

will take one class period to do the 

following:

10 minutes:

In your energy groups, you will compare 

and discuss your homework findings. In 

particular, you and other members of your 

group will discuss the sources available for 

your type of energy. You will evaluate how 

reliable the various sources of energy are 

for your school. On a scale of 1 to 4, your 

group and the other groups will assign a 

number to each energy source. If a source 

is very reliable for your school, assign the 

source a 1. Assign a 4 to sources that are 

not reliable. Consider such things as price 

and how much control the school would 

have over getting the energy, as well as 

whether the source is readily available.

Here is the scale:

1 2 3 4

Very 

reliable 

source 

Somewhat 

reliable

Not very 

reliable

Not 

reliable 

source

In your group, identify reasons for your 

assessment. For example, if biomass 

energy is rated as a very reliable source of 

energy, there should be a reliable source of 

either crop-based or forest-based energy 

nearby.

10 minutes:

Choose one student from your group to 

report your findings to the class. As a class, 

identify the three most reliable sources of 

energy for your school. A student volunteer 
12

Bioenergy Edition, http://www.naturalinquirer.org

FACTivity Extension

If you have access to the Internet in your classroom, visit http://www.naturalinquirer.org, 

Educator Resources, Lesson Plans, for an additional lesson plan. This lesson plan allows 

your students to play the role of a community deciding whether to heat its schools with 

wood chips.

will write these on the whiteboard or 

blackboard.

10 minutes:

Now repeat the groups’ exercise, 

projecting 10 years into the future. Based 

on what you know now, what do you think 

will be the most reliable source of energy 

in 10 years for your school? Why? What 

might the community need to do to develop 

that source of energy? Appoint a different 

spokesperson from your group to share the 

results of this second discussion.

If you are a Project Learning 

Tree-trained educator, you 

may use Activity # 86: “Our 

Changing World”; and #14: 

Renewable or Not?”

Additional Information 

For Your Classroom

The title of this article, “A Chip Off the Old 

Block,” is a phrase that dates to 1621. The block 

to which the phrase originally referred probably 

would have been wood or stone. The phrase 

refers to a person or a thing that comes from 

the same thing or parentage, and implies its 

similarity (http://www.phrases.org.uk/).

Additional Web 

Resources

The Fuels for Schools Program: http://

www.fuelsforschools.info/.

10 minutes:

Hold a class discussion to identify which 

three energy sources are predicted to be 

the most reliable in 10 years. A student 

volunteer will write these on the whiteboard 

or blackboard.

10 minutes:

Hold a class discussion about what the 

community might do to achieve success 

in having a reliable source of energy in 10 

years. Identify any actions you can take 

today to help achieve this goal.

If you have time, your class may 

implement some of the actions identified in 

the class discussion.
13

The Natural Inquirer • Volume 9, Number 1

Which Do You A-Door?

Comparing the Energy Needed 

to Make Wood and Steel Doors
14

Bioenergy Edition, http://www.naturalinquirer.org

Meet the Scientists

Melissa Huff, Chemical Engineer: My favorite 

science experience was when my physics 

classmates in college and I watched our 

professor dip a rubber ball into liquid nitrogen.

He then dropped it, and the ball shattered.

This is due to the temperature of the liquid 

nitrogen (-196 degrees Celsius or -321 degrees 

Fahrenheit). As you cool a gas down, the atoms 

move less and less rapidly. Eventually, the 

attractive forces between the atoms hold them 

together as a liquid. If you cool the rubber ball 

down in the liquid nitrogen, the atoms in the 

rubber become locked into position so they 

can’t move past each other. The ball becomes 

very brittle, and it can easily shatter. t

Robert Ross, Wood Engineer: My favorite 

science experience is working on research 

projects that ultimately result in technical 

advances that help people. For example, 

scientists like me do work that influences all 

of the building codes in the United States.

Building codes directly affect how homes, 

schools, churches, gymnasiums, and other 

buildings are constructed. The research you 

will read about in this article focused on 

understanding the differences between wood 

and steel doors—ultimately, it will result in 

beautiful doors, made of wood that will provide 

the security of steel doors.

s

Janet Stockhausen, Patent Attorney: My 

favorite science experience is working with 

inventors. Inventors are excited about their 

inventions, and they love to show how their 

invention works. They also love to explain why 

it works, and why it is better than everything 

else like it. Inventors like to talk about the 

potential for making the world a better place.

It is really fun to work with them. I love hearing 

the enthusiasm in their voices.

s
15

The Natural Inquirer • Volume 9, Number 1

Glossary

a as in ape

ä as in car

e as in me

i as in ice

o as in go

ô as in for

u as in use

ü as in fur

oo as in tool

ng as in sing

Pronunciation Guide

Accented syllables are in bold.

patent (pat ent): A document giving the 

exclusive right to make, use, or sell an invention 

for a number of years.

standards (stan dürds): Things set up as a rule 

or model with which other things like it are to be 

compared.

utility (u til uh te): The quality of being useful.

consumer (kän sum ür): A person or thing that 

consumes or uses something.

manufacture (man u fak chür): The making of 

goods or articles.

natural resources (na cha rôl re sôrs es): 

Supplies of things in nature that take care of a 

human need, such as oil, wood, or water.

fiberglass (fib ür glas): Glass in a fiber form 

used for making products, such as insulation.

partial (pär shul): Of a part, or in only a part.

database (dat uh bas): A large collection of 

information stored in a computer and organized 

so that it is available for use.

average (av rij): The usual kind or amount.

The number gotten by dividing the sum of two 

or more quantities by the number of quantities 

added.

extraction (ek strak shun): The act of 

extracting or pulling out by effort.

emissions (e mish ens): Something discharged 

or sent out.

solid waste (saw lid wast): Any solid or semisolid liquid, or contained gaseous materials 

discarded from industrial, commercial, mining, 

or agricultural operations; and from community 

activities, including garbage.

waterborne (wa tür bôrn): Carried in or by 

water.

kiln (kiln): A furnace or oven for drying bricks, 

pottery, or other items.

molten (môl tun): Melted by heat.

carbon dioxide equivalent (kär bun di ox

id e kwiv uh lent): A quantity that describes, 

for a given greenhouse gas, the amount of 

carbon dioxide that would have the same global 

warming potential when measured over a 

specific time period.

unit of measurement (u nit of mezh ür 

ment): A standardized quantity of a physical 

property, such as inches, meters, kilograms, etc.

Thinking About Science

When scientists want to compare things, they must use a common language. 

In this research, the scientists wanted to compare the environmental impact of 

making two different kinds of doors. The scientists went to the International 

Organization for Standardization (stan dürd uh za shun) for help. This 

organization creates standards for a wide variety of products and processes. The 

organization reported that two products can be compared if they provide the same utility to a 

consumer. The scientists decided that they could compare two different doors if both of those 

doors could be used to enter a house. Based on this standard, could you compare the utility of a 

plastic and metal fork? Why or why not?
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Bioenergy Edition, http://www.naturalinquirer.org

Thinking 

About the 

Environment

Every product you buy 

was produced using energy. 

Every process used to create 

products also creates waste. In this research, 

the scientists wanted to compare the amount 

of energy used and amount of waste created 

in the manufacture of two different types of 

doors. This kind of comparison is called a lifecycle inventory (figure 1). Most life-cycle 

inventories include the amount of energy used 

and waste created from when the raw materials 

are gathered to make the product to when a 

consumer no longer wants and disposes of the 

product. In this research, the scientists were 

interested only in the energy used and waste 

created until the time the doors were ready to 

be shipped to a store. 

Figure 1. Life-cycle inventory. This shows the 

entire life-cycle inventory process. The part of 

the life-cycle inventory used in this research to 

compare the utility of two different kinds of doors 

is also shown. The result of a life-cycle inventory 

is a measurement of the environmental impact 

of one or more products. (Image courtesy of 

Franklin Associates http://www.fal.com) 

Figure 2. The Forest Products Laboratory.

Introduction

The Forest Products Laboratory, located in 

Madison, Wisconsin, is a place where scientists 

work to develop wood products for human 

use (figures 2 and 3). The scientists at this 

laboratory develop processes for making wood 

products that use as few natural resources 

as possible. One of the wood products they 

developed was a wood door. The door was 

made using a process to strengthen the wood 

by including a small amount of fiberglass. The 

fiberglass made the wood door strong enough 

to be used in place of a steel door.

Figure 3. Madison, Wisconsin.
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The Natural Inquirer • Volume 9, Number 1

The scientists believed that wood doors 

and steel doors provide the same utility to 

a consumer (figures 4 and 5). If that is the 

case, they wondered which door would use 

less energy and create less waste up to and 

including the manufacturing process. To answer 

their question, the scientists conducted a 

partial life-cycle inventory to compare the two 

doors. In this article, the manufacturing process 

includes gathering and processing the raw 

materials for each door. As an example, for the 

wood door this includes harvesting the tree and 

transporting it to a mill.

Figure 4. Wood door. Photo courtesy of Lowe’s. Figure 5. Steel door. Photo courtesy of Lowe’s.

Reflection Section

b	 In your ownwords, state the question the

scientistswanted to answer.

b	 Where do peoplegetthe rawmaterials they

need tomanufacture products?

Method

The scientists first had to identify which 

raw materials are needed for a wood door 

made with fiberglass and which materials are 

needed for a steel door. They then had to 

identify where those raw materials come from. 

They made a diagram of the process used to 

manufacture a steel door and a wood door 

(figures 6a and 6b).

The scientists also had to identify how much 

energy is used for gathering raw materials and 

manufacturing each door, and how much waste 

is created in each process. 

The scientists collected their information 

from a special database. The database is kept 

by a company that does a variety of life-cycle 

inventories. The scientists collected information 

about the average energy used to manufacture 

each kind of door. The categories of information 

collected were:

1. Extraction, transportation, and processing the 

fuels used in all the manufacturing processes.
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Bioenergy Edition, http://www.naturalinquirer.org

Wood Door Manufacturing Process

Process

Harvest Trees

Transport to Sawmill

Wood Dried in Kilns

Wood Cut in Sawmill

Epoxy Applied to Wood

Completed Wood Door:

Transported to

Retail Store

Type of Energy Used

Fossil Fuel

Fossil Fuel

Natural Gas, Fossil Fuel, and Electricity

Electricity and Fossil Fuel

Electricity and Fossil Fuel

Fossil Fuel

Steel Door Manufacturing Process

Process

Mining Raw Materials

Transport to Refinery

Materials Heated in Blast Furnace

Materials Cooled in Cold Reduction Mill

Machines Mold and Press Material

into Sheet Metal

Sheet Metal Transported

to Fabrication Mill

Cutting and Forming

Sheet Metal into

Door Shape

Weld Metal Sheets Together

Completed Steel Door

Transported to Retail Store

Type of Energy Used

Fossil Fuel and Electricity

Fossil Fuel

Fossil Fuel and Electricity

Fossil Fuel and Electricity

Fossil Fuel and Electricity

Fossil Fuel

Fossil Fuel and Electricity

Fossil Fuel and Electricity

Fossil Fuel

Figure 6a. A diagram, or flow chart, of the manufacturing process of a wood door.

Figure 6b. A diagram, or flow chart, of the manufacturing process of a steel door.
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The Natural Inquirer • Volume 9, Number 1

2. Extraction, transportation, and processing 

the raw materials used in all the 

manufacturing processes.

The scientists also collected information 

about the average amount of waste 

products, including emissions, resulting from 

the manufacture of each kind of door. The 

categories of information collected were: 

1. Air emissions.

2. Solid waste.

3. Waterborne waste.

Before a wood door can be manufactured, 

the raw materials for the door must be 

collected. For a wood door, trees are the main 

raw material used. When trees are harvested, 

energy is used and pollutants are produced. 

Pollutants are produced from the cutting 

equipment and machinery, and include more 

than air emissions (figure 7). Soil erosion can 

result in water pollution in the form of soil 

particles in the water. The cut logs are taken 

to a sawmill, the bark is taken off, the logs are 

cut into boards, and then dried in a kiln. The 

wood door is strengthened with fiberglass. All 

of these processes require energy and result in 

environmental emissions.

Before a steel door can be manufactured, 

mining for raw materials must be done. 

Mining for iron ore, zinc, limestone, and coal 

is necessary to manufacture steel (figures 8a 

and 8b). Most of these materials are placed in a 

blast furnace to produce a substance called pig 

iron. The molten pig iron is further heated and 

poured into molds, where it is cooled and made 

Figure 7. Wood harvesting operation.

Figures 8a and 8b. Surface mining operations.

Photos courtesy of Peter Robey Mining 

Photography.
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into sheet metal. The sheet metal is galvanized 

(gal van izd) by being coated with a thin layer 

of zinc. This process protects the sheet metal 

from rust. During manufacture, the inside of 

steel doors are filled with a material, a form of 

polystyrene (paw le sti ren), like Styrofoam. All 

of these processes require energy and produce 

environmental emissions.

When steel doors are manufactured, the 

sheet metal must be cut, welded, stamped, and 

the door filled with polystyrene. Then the door 

must be painted. While these processes create 

a lot of emissions and solid wastes, some of the 

solid waste products can be recycled.

The scientists calculated how much energy 

is used and how much emissions are created in 

the manufacture of each door. The information 

they collected included: 

1. Number of airborne substances released.

2. Number of waterborne substances released.

3. Total energy use in gigajoules (gig uh julz).

4. Solid waste in kilograms.

5. Greenhouse gas emissions in kilograms of 

carbon dioxide equivalents.

Reflection Section

b	 The scientists included the energy used and

emissions producedwhen the rawmaterials

were collected, aswell as themanufacture of

each door.Why do you think they included

the gathering ofrawmaterials in the life-cycle

inventory?

b	 Do you think the scientists found ittakesmore

energy tomanufacture awood door or a steel

door?Why?

Findings

The scientists calculated amounts for 44 

airborne emissions released to the environment, 

including 3 greenhouse gases. They also 

calculated amounts for 32 waterborne wastes 

released to the environment, as well as solid 

wastes and the amount of energy used in the 

manufacturing process. Tables 1–5 show the 

results of their research.

Table 1. Number of airborne emissions produced by the manufacture of a wood door and a steel 

door.

Airborne emissions for which: Number of emissions

Steel door was higher 31

Emissions were reported for steel door but not for wood door 5

Steel door was lower 7

Emissions were reported for wood door but not for steel door 0

No difference found 1

Table 2. Number of waterborne wastes produced by the manufacture of a wood door and a steel 

door.

Waterborne wastes for which: Number of emissions

Steel door was higher 28

Emissions were reported for steel door but not for wood door 4

Steel door was lower 0

Emissions were reported for wood door but not for steel door 0

No difference found 0
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The Natural Inquirer • Volume 9, Number 1

The amount of energy used in the 

manufacture of a steel door and a wood door 

was measured in gigajoules (GJ) (table 3). One 

GJ is equal to about 278 kilowatt hours (kWh), 

or 238,000 nutritional calories. The joule is a 

member of the international system of units 

(SI), the modern form of the metric system.

Table 3. Total amount of energy, measured in 

GJ, used in the manufacture of a wood door 

and a steel door.

Total energy (GJ)

Steel door 2.17

Wood door 0.10

Number Crunches

b	 Let’s say the average daily energy use in a

home is 15 kWh.Howmany dayswill ittake

before the amount of energy used in that

home is equalto the total amount of energy

used tomanufacture a steel door?How

many dayswill ittake to equalthe amount of

energy used tomanufacture awood door?

(Remember:1GJ is equalto about 278 kWh.)

b	 While doingvigorous exercise such

as running, an adult burns about100

nutritional calories each hour.Howmany

hourswill ittake to burn 1GJ of energy?How

many days of vigorous exercisewill ittake

the adultto burn 1GJ of energy?Howmany

days of vigorous exercisewill ittake forthe

adultto burn the amount of energy used in

the production of a steel door and awood

door? (Remember,1GJ is equalto 238,000

nutritional calories.)

b	 One kilogramis equalto about 2.2 pounds.

Create your own table 4 using pounds,

instead of kilograms, as the unit of 

measurement.

The amount of solid waste produced in the 

manufacture of the doors was measured in 

kilograms (kg). Table 4 shows the amount of 

solid waste produced in the manufacture of 

each door, measured in kg.

Table 4. Amount of solid waste produced in 

the manufacture of a wood door and a steel 

door.

Total amount

of solid waste 

produced (kg)

Steel door 22.3

Wood door 0.51

Table 5 presents the potential of three 

greenhouse gases to contribute to global 

warming during the manufacture of each door. 

This amount is expressed in relation to the 

global warming potential of carbon dioxide over 

a 100-year period, which is set at 1. In other 

words, if another greenhouse gas has a value 

of 2, it has twice the global warming potential 

of carbon dioxide over a 100-year period. The 

gases listed in table 5 are the three largest 

contributors to global warming. 
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Bioenergy Edition, http://www.naturalinquirer.org

Table 5. The amount of greenhouse gases produced during the manufacture of wood and steel 

doors.

Gas Global warming 

potential of gas 

Steel door (kg of 

carbon dioxide per 

door)

Wood door (kg of 

carbon dioxide per 

door)

Carbon dioxide 1 135 5.11

Methane 23 5.87 0.13

Nitrous oxide 296 0.10 0.0051

TOTAL No Total 141 5.25

Reflection Section

b	 Examine tables 1–5.What conclusion can you

make aboutthe production of a steel doorin

comparisonwith the production of awood

door?

b Basedon the findings you have justread,what

would you predict aboutthe environmental

impact ofmanufacturing a steeltable

comparedwithmanufacturing awood table?

Discussion

According to this research, the manufacture 

of a steel door results in more air emissions, 

more waterborne pollutants, and more solid 

waste than the manufacture of a wood door. 

A steel door also requires more energy in 

its manufacturing and results in a greater 

potential to contribute to global warming. The 

manufacture of a steel door, in fact, consumes 

21 times the amount of total energy and 

produces over 40 times the amount of solid 

waste compared to the manufacture of a

wood door.

Reflection Section

b	 This life-cycle inventory showed thatmore energy is used andmorewaste produced in the

manufacture of a steel door.Whatmight be one advantage of using a steel doorinstead of awood

doorin your home?Do you think this advantage of using a steel door outweighs the disadvantage of

its greater environmental impact?Why orwhy not?

b	 If youwere employed by a home improvement store in your community,whatwould you tell a

homeownerwho has come into your storewanting to buy a newdoorfor his or her home? 

From: Knight, L., Huff, M., Stockhausen, J. I., and Ross, R. J. 2005. Comparing energy use and environmental emissions 

of reinforced wood doors and steel doors. Forest Products Journal, 55 (6): pp. 48-52, http://www.fpl.fs.fed.us/documnts/

pdf2005/fpl_2005_knight001.pdf.
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The Natural Inquirer • Volume 9, Number 1

FACTivity

Time Required

One class period

Materials Needed

1. One large raw potato

2. One 10-ounce bag of plain potato 

chips

3. One blank sheet of paper and a pencil 

for each group

The research question you will answer 

by doing this FACTivity is: “Does a baked 

potato or a 10 ounce bag of potato chips 

require more energy when it is produced 

for human consumption?” This question 

is similar to the question asked by the 

scientists in this research, except the 

scientists compared two doors instead of 

two kinds of potatoes. You may want to reread the last paragraph of the “Introduction” 

to remind you of the scientists’ research 

question.

When the scientists compared doors, 

they compared doors of equal utility. This 

means that both doors could serve the 

same purpose for an individual. When you 

compare two kinds of potatoes, are you 

comparing products that serve the same 

purpose for an individual? How do the two 

types of products (doors and potatoes) 

compare?

Method

The method you will use to answer the 

research question is:

Consider the following: Just as doors 

have a premanufacturing stage and a 

manufacturing stage, the two potato 

products have a preprocessing and a 

processing stage. Potatoes must be planted, 

grown, dug, and transported to a facility for 

processing before they can be shipped to a 

supermarket shelf.

In small groups, brainstorm the steps that 

must be taken before potatoes are shipped 

to a facility for processing. For both kinds of 

potato products, this preprocessing stage 

will be the same. Once the potatoes get to 

their facilities for processing, each type of 

potato will be processed differently. Write 

down the steps that must be taken, and 

identify the kind of energy needed for these 

steps.

Example:

STEP ENERGY NEEDED

Plow field before 

planting

Diesel fuel for 

machinery

Plant potatoes Diesel fuel for 

machinery

Once you have done this, you must 

now consider what kind of processing is 

needed to prepare each potato product 

and transport it to a store. In the case of 

the potato, processing may only include 

cleaning, sorting, bagging, and transporting.

It takes more steps to create potato chips, 

even before they are placed in bags for 

shipping to stores. Although you may have 

never been to a potato chip processing 

plant, see if your group can imagine what 

steps must be taken from the time a potato 

arrives at the plant to the time it leaves 

the plant as a bag of potato chips. Use the 

same format to record the steps that you 

used when you imagined the steps required 

to get a potato to the processing plant.

Remember to do this for a potato, as well as 

for the potato chips.

Remember that you must consider all 

steps needed before human consumption 

for both kinds of potatoes.
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Bioenergy Edition, http://www.naturalinquirer.org

You should now have a good idea of 

the steps and types of energy required to 

process a potato and a bag of potato chips 

for human consumption.

As a class, compare the steps each 

group has developed for each type of 

potato. Discuss the amount of energy 

that might be required by each type of 

potato product. Although you will not know 

exactly how much energy each type of 

potato product requires for processing, you 

should have a good idea of which type of 

potato processing requires more energy.

Now answer your research question: 

Which potato product requires more 

energy to be processed for human 

consumption?

FACTivity: Go Outdoors

Time required

One class period

Materials needed 

One 12” new or used clay pot

One 12” new or used clay saucer

One 12” new or used plastic pot

One 12” new or used plastic saucer

One new or used metal trash can lid 

(with no holes)

One large new or used sturdy plastic 

bucket

Acrylic sealant (brush-on or spray can)

Paint brush (if using brush-on sealant)

Heavy-duty outdoor glue

24” rope

Two bricks (one preferably with holes)

Flat rock, about 4” in diameter

In this FACTivity, you will answer the 

question: How does the energy use 

involved in the construction of three homemade bird baths compare when they are 

constructed?

This FACTivity involves a partial lifecycle inventory. The research article you 

read described a partial life-cycle inventory 

involving the manufacturing process up 

to production of the product. Complete 

life-cycle inventories include use, reuse, 

recycling, or disposal of the product. You will 

construct three bird baths from either new or 

recycled materials.

Method

The method you will use to answer the 

research question is: 

Your class will construct three different 

bird baths using either new or used 

materials. After construction, each bird bath 

will be compared on the basis of whether 

its construction involved new or recycled 

materials.

Birdbath #1: Clay pot, clay saucer, sealant

Birdbath #2: Plastic pot, plastic saucer, 

glue, flat rock

Birdbath #3: Plastic bucket, metal trash 

can lid, bricks, rope

Divide into three groups. Each group will 

construct one birdbath. Construction and 

placement should occur at about the same 

place. Place your birdbaths in an area away 

from bushes or other low vegetation, but 

close to a tree if possible. Low vegetation 

may hide predators, and trees will provide a 

place for birds to perch.
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The Natural Inquirer • Volume 9, Number 1

Birdbath #1: 

1. The day before, seal the clay saucer 

with sealant.

2. Turn the clay pot over and position it 

where you want to place the birdbath.

3. Place the clay saucer on the overturned pot.

4. Fill the saucer with water. Place fresh 

water in the saucer every day.

Birdbath #2:

1. Turn the plastic pot over and position 

it where you want to place the 

birdbath.

2. Glue the plastic saucer on the overturned pot.

3. Place a flat rock in the center of the 

birdbath for stability.

4. Fill the saucer with water. Place fresh 

water in the saucer every day.

Birdbath #3:

1. Place the plastic bucket where you 

want to place the birdbath. This 

birdbath should be placed where 

there is complete shade during the 

hottest part of the day.

2. Place one of the bricks in the bottom 

of the bucket for stability.

3. Measure the bucket’s height and 

subtract 4 inches. Cut the rope to this 

length.

4. Tie one end of the rope to the handle 

on the trash can lid.

5. Tie the other end of the rope around 

the second brick.

6. Place the trash can lid upside down 

on the bucket, letting the brick dangle 

inside the bucket. The brick will 

provide stability for the trash can lid.

7. Fill the trash can lid with water. Place 

fresh water in the lid every day.

Now that you have made your birdbaths, 

it is time to compare them. Each group will 

assess its own birdbath. This can be done 

inside the classroom.

Make a list of the materials used for your 

birdbath. Note if the material is new or used.

You may use the example below to create 

your chart.

Type of Birdbath: 

MATERIAL NEW OR 

USED?

NUMBER OF 

POINTS

Clay pot New

Trash can lid Used

Glue New

TOTAL 

POINTS -----------------

If the material used is new, give it one 

point. If the material is used, give it a zero.

Now add the points for your birdbath. If 

your birdbath was built entirely from used 

materials, it should have received zero 

points.

As a class, compare the point values of 

each birdbath. What do those values tell you 

about the energy needed to construct each 

birdbath? What does this comparison tell you 

about the energy involved in the use of new 

and used materials for construction?

If you are a Project Learning Tree-trained educator, you 

may use Activity #69: “Forest for Trees.”
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Comparing the Cost 

of Using Trees to 

Heat Buildings

Chip and Truck

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27

The Natural Inquirer • Volume 9, Number 1

Meet the Scientists

Dr. Silverstein, Landscape Ecologist: 

I enjoyed studying coyotes (ki ots) in 

Yellowstone National Park because it involved 

trying to understand the mysteries of the 

daily life of a wild animal. I watched coyotes’ 

behavior, tracked their movements, and 

recorded their interactions with other animals. I 

got to know them better than I ever could from 

reading books or watching television. There is 

no better experience than getting out in nature 

to learn.

t s

Dr. Loeffler, Forest Economist: My favorite 

science experience is canoeing brackish 

water areas in the Chesapeake Bay, observing 

estuary (es chu wair e) wildlife like birds, crabs, 

snakes, and fish. An estuary is a body of water 

at the mouth of a river with open access to the 

ocean and under the influence of ocean tides.

Dr. Jones, Research Forester: My favorite 

science experience is making a scientific 

discovery that people find useful. Recently, 

we discovered that using cut, small trees for 

energy reduces the production of greenhouse 

gases by 50 percent compared to burning the 

small trees in the forest.

t

s

Dr. Calkin, Forest Economist: My favorite 

science experience is working with forest 

fire managers to apply economic concepts.

Applying these concepts helps us understand 

how best to balance taxpayers’ costs of 

managing wildfires against the changes to 

natural resources that come from wildlfires.
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Meet the Scientists

Dr. Zuuring, Mathematical Scientist: My 

favorite science experience is being a judge 

at the Montana Science Fair held annually in 

March. I get to interact with students from 

grades 6 to 12 and learn about their science 

projects. t

s

Mr. Twer, Landscape Ecologist: My favorite 

science experience is working with a Stirling 

engine. A Stirling engine is an engine that 

can use any heat source to create energy.

A Stirling engine is quieter and requires less 

maintenance than the kind of engines used 

today. In the future, we may be using Stirling 

engines for more of our energy needs.

Glossary:

a as in ape

ä as in car

e as in me

i as in ice

o as in go

ô as in for

u as in use

ü as in fur

oo as in tool

ng as in sing

Pronunciation Guide

Accented syllables are in bold.

economist (e kän uh mist): A scientist who 

studies economics. Economics is the study 

of the way goods, services, and wealth are 

measured, produced, distributed, and used.

variables (ver e uh bulz): Things that can vary 

in number or amount.

simulate (sim yoo lat): To create the effect 

or appearance of something for purposes of 

evaluation.

abstract (ab strakt): Not associated with a 

specific instance; theoretical.

data (dat uh): Facts or figures studied in order 

to make a conclusion.

equation (e kwa shun): A written statement 

that indicates the equality of two algebraic 

expressions.

forest managers (för est mä ni jürz): Skilled 

individuals who take care of natural resources.

wildfire (wild fir): An uncontrolled wildland fire 

started naturally or by careless human action.

facility (fuh si luh te): Something that is built to 

serve a particular purpose.

thermal (thür mul): Of, related to, or caused by 

heat.

revenues (reh vuh nooz): The total incomes 

produced by a given source.

nutrients (noo tre ents): Any of the substances 

found in food that are needed for the life and 

growth of plants and animals.
29

The Natural Inquirer • Volume 9, Number 1

net revenues (net reh vuh nooz): What is left 

of the revenue after costs are paid.

economically (e ko nom ik le): Having to 

do with the management of money in a home, 

business, or government.

average (av rij): The usual kind or amount.

The number gotten by dividing the sum of two 

or more quantities by the number of quantities 

added.

Glossary:

Thinking 

About Science

Some scientists study 

complex systems. Complex 

systems are ones in which 

many different variables are 

related and affect one another. An example 

of a complex social system is your school or 

even your classroom. An example of a complex 

natural system is a forest, a pond, or even a 

single tree. Scientists use computer models to 

help them better understand complex systems. 

A computer model is a computer program 

that attempts to simulate an abstract model 

of a system. The computer model contains 

the assumed relationships between variables. 

When data are entered into the model and 

the computer program is run, scientists 

can see what might happen under different 

circumstances. An equation in algebra is a 

simplified version of a computer model. 

Thinking 

About the 

Environment

Forest managers have a 

number of choices when they 

manage an area of forest. Each 

possible choice creates a different outcome. You 

face a similar situation in your own life. Think 

about one situation in your life where a different 

choice would have created a different outcome. 

In this research, the scientists wanted to help 

forest managers understand the outcomes of 

different choices.

When trees are cut from a forest, the 

largest trees may be used for lumber and other 

wood products. The smaller trees may be left 

standing or cut to reduce the threat of wildfire. 

After being cut, small trees may be piled 

together and burned. Another option is to cut 

the small trees into pieces, called woodchips, 

and take them to a special facility. At this 

facility, the woodchips are burned to create 

thermal energy that heats buildings.

As you may know, the cost of oil goes up 

and down. The supply of oil is less secure. One 

option for fuel is to use woodchips to provide 

energy. In this study, the scientists compared 

the cost of using woodchips for thermal energy 

with the cost of burning the small trees in piles 

in the forest. 

Introduction

In the Western United States, many of the forests have too many small trees (figure 1). These 

small trees increase the risk of wildfire. Forest managers, therefore, want to remove the small trees. 

Some scientists believe these small trees may be a good source of fuel. To explore this possibility, 

a program called “Fuels for Schools” was created in Montana. As a part of this program, a special 

facility was built near the schools. This facility takes woodchips from surrounding forests and burns 

them to create thermal energy. Schools were chosen because they are public buildings and might 

benefit from being able to save fuel costs.
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Bioenergy Edition, http://www.naturalinquirer.org

When small trees are cut into woodchips 

and hauled by a truck to the facility, money is 

spent on fuel to cut the woodchips and haul 

them (figures 2a and 2b). When small trees 

are burned instead, less money is spent on fuel. 

The scientists in this study wanted to compare 

the costs of and revenues gained from using the 

small trees for thermal energy with the cost of 

piling and burning the small trees. In both cases, 

the larger trees were sold to a mill to be made 

into lumber.

Figure 1. Western forest with too many small 

trees.

Are Forest Fires Bad?

Many people think forest fires are always 

a bad thing. Before the United States was 

settled by Europeans, fire was a normal part of 

a forest’s life. Fire can provide many benefits to 

a forest. Fire helps return nutrients to the soil 

as it burns leaves, small branches, and bark on 

the forest floor. This also helps to reduce fuel 

so fire is not as likely in the next year. When 

the forest floor is opened by fire, sunlight can 

reach the ground, enabling new plants and 

trees to get their start.

Fires usually kill weakened trees. These 

are trees with destructive insects or diseases.

When weakened trees are killed, the spread 

of destructive insects and diseases is slowed.

Without fire, too many trees can grow in a 

forest. When too many trees are present, it is 

more difficult for trees to grow to a large size.

The smaller trees increase the risk of a large 

wildfire. Removing smaller trees where there 

are too many makes it possible to have the 

type of fire that benefits a forest.

You can see that fire is not always a bad 

thing for a forest. In fact, occasional fires can 

help keep a forest healthy.

Figures 2a and 2b. Diesel fuel must be used to cut woodchips and haul them.
31

The Natural Inquirer • Volume 9, Number 1

Reflection Section

b	 What question did the scientistswantto answer?

b What are the sources ofthe two types offuelbeingcompared in this study?Which ofthese fuels is

renewable?

Method

The scientists selected areas in the Bitterroot 

National Forest in western Montana (figures 

3 and 4). These areas provided everything 

the scientists needed to answer their question. 

Forest fires had not been allowed to burn for 

many years in these study areas, so there 

were a lot of small trees growing. More people 

were moving to the Bitterroot area, so there 

was a need for energy to heat buildings. There 

were two facilities in the area that could turn 

woodchips into thermal energy. There was also 

a mill that could take the larger trees and turn 

them into lumber for wood products.

Figure 3. The Bitterroot National Forest in western Montana.

What is d.b.h.?

Diameter at breast height, 

or d.b.h., is a standard way 

to measure the size of trees.

The diameter of a tree’s trunk 

is measured at 4.5 feet, or 

1.37 meters, from the forest 

floor. If the tree is on a hill, the 

measurement is made from 

the uphill side of the tree. What 

would happen if the diameter 

of tree trunks was measured 

anywhere a forester felt like 

measuring it? Would such a 

measurement be useful? Why 

or why not?

Using a computer program, the scientists 

simulated cutting trees with a d.b.h. of 7 inches 

or less. (See sidebar to learn about d.b.h.) The 

scientists also simulated cutting some of the 

larger trees, which could then be sold for wood 

products. The scientists estimated the costs of 

and revenues gained from cutting small trees 

into woodchips. They estimated the costs of 

and revenues gained from hauling the chips 

to one of the two facilities to create thermal 

energy. They also estimated the revenues 

gained from selling the larger trees for wood 

products. The scientists then estimated the 

costs of piling the small trees and burning them 

after they were cut.
32

Bioenergy Edition, http://www.naturalinquirer.org

Figure 4. Landscape of the Bitterroot National 

Forest in western Montana.

The scientists created an equation to 

include all of the costs and revenues. In their 

equation, the small trees could be treated in 

one of four ways: (1) Cut down and burned; 

(2) Cut down, cut into woodchips, and hauled 

to a facility in Darby, Montana; (3) Cut down, 

cut into woodchips, and hauled to a facility in 

Frenchtown, Montana; or (4) Cut down, cut 

into woodchips, and hauled to either Darby 

or Frenchtown. Each of these options costs 

something. For example, it takes fuel to cut 

down trees. It also takes fuel to cut trees into 

woodchips and drive them to a facility. In each 

situation, the larger trees were cut down and 

hauled to a mill to be turned into lumber.

The scientists had to calculate all of the costs 

and revenues. To estimate hauling cost, for 

example, they had to multiply the number of 

miles driven times the per mile cost of owning 

and operating a truck, including the fuel used. 

To calculate revenue, they had to estimate the 

number of tons of woodchips cut from each 

area, and multiply the number of tons by how 

much money they would get from each ton.

When the scientists had all of the numbers 

they needed, they entered the numbers into 

a computer program. The computer program 

compared burning small trees with cutting and 

hauling woodchips from the study areas in the 

forest. The computer program also contained 

the equation that would subtract the costs and 

add the revenues for each of the four options. 

Reflection Section

b	 Whenever peoplemake a choice to do one

thing ratherthan something else,there are

costs and benefits to each choice. Think about

a choice you recentlymade. Identify the costs

and benefits ofthat choice, comparedwith

another choice you could havemade instead.

Rememberthat costs involvemore than just

money.For example,time, or even the loss of a

friendship, can be considered a cost.

b In this study,there is one costin particular

that continues to rise.Whatis that cost?

Howdo you think this costmight affectthe

scientists’results ifthey did this study next

year?

Findings

The scientists discovered the distance 

woodchips were hauled was the most 

important variable to consider when choosing 

between burning small trees and cutting 

woodchips. The farther the distance between 

where the trees were cut and the thermal 

energy facility, the more costly it was to 

cut woodchips for thermal energy. When 

woodchips could be hauled to either Darby 

or Frenchtown, the net revenues were higher. 

When all chips had to be sent to Darby, there 

was still net revenue, but not as much. When 

all chips had to be sent to Frenchtown, the cost 

went up and net revenue went down. This 
33

The Natural Inquirer • Volume 9, Number 1

was because Frenchtown was not as centrally 

located as Darby to the forested areas (figure 

5). In this case, it made more sense economically

to burn more of the small trees at the forested 

sites. 

Figure 5. Darby was more centrally located 

within the forested area.

Figure 6 shows the average cost and 

revenue per acre for each step in the process. 

Costs involve cutting small and large trees, 

burning small trees or cutting them into 

woodchips, and hauling the trees and 

woodchips. Revenues are gained from selling 

the woodchips and selling the larger trees.

Figure 6. Costs, benefits, and resulting value for 

an average acre of forested land.

-1500

-1000

-500

0

500

1000

1500

2000

2500

3000

3500

4000

Cost of

removing

trees and

chips

Cost of

hauling

trees and

chips

Revenue

from 

selling

trees

Revenue

from 

selling

chips

Total

net

value

Dollars per acre

Reflection Section

b	 Look atfigure 6.Where doesmost ofthe

revenue come fromin this situation?

b Itmakes sense to cuttrees intowoodchips

when facilities that can usewoodchips

are located close by.However,fewofthese

facilities currently exist. As fuel costs rise, in

whatwaysmightthis situation change?

Discussion

Removing small trees from western forests 

can help reduce the risk of future wildfires. Such 

cutting also helps return the forest to a more 

natural condition, in which fires occasionally 

remove small trees by burning. Removing small 

trees, therefore, can help restore the health of a 

forest.

This research showed that cutting small 

trees into woodchips for energy produces 

revenue when there is a woodchip facility 

nearby. This research also showed the distance 

between the forest area and the facility was 
34

Bioenergy Edition, http://www.naturalinquirer.org

important. The further the distance between 

them, the less revenue was gained. 

The scientists observed that to gain enough 

revenue from woodchips, more woodchip 

facilities will be needed close to forested areas. 

They noted, however, that as small trees are 

removed from western forests, forest health 

is improved. As forest health improves, fewer 

small trees will grow. This will reduce the future 

supply of small trees for woodchip facilities.

Reflection Section

b	 The scientists pointed out a dilemma that

could be faced in the future.Whatis that

dilemma?

FACTivity

In this FACTivity, you will answer the 

question: “Do rising fuel prices affect the 

choices we make?”

The method you will use to answer this 

question is:

Divide your class into groups of four 

students. Each group is given an imaginary 

$100 to spend on a Saturday, or $25 per 

student. If your group overspends, the 

money has to come out of your pockets 

equally. If your group under-spends, you 

can evenly split and keep the left-over 

money. All expenses are shared equally.

One of your options is to go to an 

amusement park. The amusement park is 

60 miles away one way, and your group is 

riding in a vehicle that gets 30 miles to the 

gallon. The group must pay for the fuel. The 

admission price per student is $15. You will 

have to eat lunch and buy whatever drinks 

and snacks you want once you get into the 

park. You estimate that this will cost each 

of you $10. On the day you plan to go, a 

nationally famous hip-hop band will be 

giving a concert, and your admission price 

includes admission to the concert. This is a 

concert that everyone you know will be at.

An alternative activity for your group on 

that same day is a concert featuring a local 

college rock band. This is not one of your 

group’s favorite bands, but the music is 

okay. The band is playing just 15 miles away 

one way, and the admission price is $5 per 

student. You would be riding in the same 

vehicle as before, and you have to pay for 

the fuel. Lunch will be available at a cost of 

$8 each.

Now, you will consider all of your options 

and make a decision about which activity 

you will do as a group. You will consider 

the options under four different situations.

In these situations, everything is the same 

except the price of fuel.

Calculate your group’s fixed costs first.

Those are the costs that will not change, 

such as the price of admission and of lunch.

You can complete the chart on the next 

page.

Adapted from: Silverstein, R. P., Loeffler, D., Jones, J.

G., Calkin, D. E., Zuuring, H. R., and Twer, M. (2006).

Biomass utlization modeling on the Bitterroot National 

Forest, In: Andrews, P. L. and Butler, B. W., compilers.

Fuels management—How to measure success.

Conference Proceedings, 28-30 March 2006; Portland, 

Oregon, Proceedings RMRS-P-41. Fort Collins, CO: 

U.S. Department of Agriculture, Forest Service, Rocky 

Mountain Research Station. http://www.fs.fed.us/rm/

pubs/rmrs_p041/rmrs_p041_673_688.pdf
35

The Natural Inquirer • Volume 9, Number 1

Admission 

price per 

student

Admission 

price for 

group

Lunch price 

per student

Lunch price 

for group

Subtotal 

cost for 

group

Number 

of gallons 

of fuel for 

round trip

Amusement 

park and hiphop concert

Rock concert

Now, complete the next two charts.

Fuel: $2.00/gal Fuel: $2.75/gal Fuel: $4.20/gal Fuel: $4.50/

gal

Cost of fuel for round 

trip to amusement park 

and hip-hop concert

Cost of fuel for round 

trip to rock concert

Fuel: $2.00/gal Fuel: $2.75/gal Fuel: $4.20/gal Fuel: $4.50/

gal

Subtotal cost for group—

Amusement park (from 

first chart, same value 

for all columns)

Cost of fuel for round 

trip to amusement park

(from second chart)

Total cost for amusement park trip

Subtotal cost for group—

Rock concert (from first 

chart, same value for all 

columns)

Cost of fuel for round 

trip to rock concert

(from second chart)

Total cost for rock

concert trip
36

Bioenergy Edition, http://www.naturalinquirer.org

If you are a Project Learning 

Tree-trained educator, you 

may use Activity # 53: “On 

the Move” or Activity #82: 

“Resource-Go-Round” or 

Activity #51: “Make Your

Own Paper.”

As a group, decide which activity you 

would choose under the four different 

prices of fuel. If the amusement park 

was 20 miles away, would your decision 

change? What if it were 100 miles away?

How has your discussion changed as a 

result of increasing fuel prices? Has your 

decision changed as a result of increasing 

fuel prices? If so, why? If not, why not?

Hold a class discussion about your 

group’s decisions. Now discuss whether 

you or and your family are making any 

changes as a result of changing fuel 

prices. What changes are being made, 

if any? What are some advantages and 

disadvantages of having to make these 

changes?

How were your options like the 

simulated options presented in this article? 

How were they different?

Additional information 

for your classroom:

The title of this article is “Chip and Truck.” 

This title is a take-off on the phrase “Nip and 

Tuck.” The phrase, “Nip and Tuck” was first 

used in the 19th century. It means “a close 

result in a race or contest.” You might ask 

your students to compare and contrast the 

phrase “Nip and Tuck” with the results of 

the article, “Chip and Truck” (http://www.

phrases.org.uk/).
37

The Natural Inquirer • Volume 9, Number 1

Predicting the Future Energy 

Benefits of Tree Crowns

How 

Now 

Round 

Crown?

How 

Now 

Round 

Crown?

37

The Natural Inquirer • Volume 9, Number 1
38

Bioenergy Edition, http://www.naturalinquirer.org

Meet the Scientists

Andy Scott, Soil Scientist: I enjoy science 

because I get to continually learn about things 

and help others learn. Every experiment has 

three great parts for me. First, each experiment 

means I’m doing something new, either in a 

new place or in a new way. Continually doing 

new things makes science exciting. Second, 

by doing science I discover new things that 

help us understand forests and soils and how 

to best manage them. Analyzing data can be 

very rewarding when it tells you something you 

didn’t already know (think “Eureka!”). Finally, 

my favorite part of science is helping others 

understand the forest. I know I’ve done a good 

job when I’ve helped somebody else learn 

something.

 t

s

Tom Dean, Soil Scientist: My favorite 

science experience is discovering how trees 

work: how they stand up, how they grow, 

and how they withstand changes in the 

environment year after year.

Glossary:

a as in ape

ä as in car

e as in me

i as in ice

o as in go

ô as in for

u as in use

ü as in fur

oo as in tool

ng as in sing

Pronunciation Guide

Accented syllables are in bold.

data (dat uh): Facts or figures studied in order 

to make a conclusion.

economically (e ko nom ik le): Having the 

characteristic of little waste or at a savings.

crowns (krowns): The top parts of things.

resource (re sôrs): Any physical or virtual thing 

of limited availability, or anything used to help 

one earn a living.

renewable (re nu uh bool): Capable of being 

made like new again.

nutrients (noo tre ents): Any of the substances 

found in food that are needed for the life and 

growth of plants and animals.

hectare (hek tär): A metric measure of land 

area equal to .405 acre.

megawatt hours (meg uh wat ow ürs): one 

joule of energy per second. If a 100-watt light 

bulb is turned on for 1 hour, the energy used is 

100 watt-hours.

biomass (bi o mas): All the living or once-living 

things in a particular area.

average (av rij): The usual kind or amount.

The number gotten by dividing the sum of two 

or more quantities by the number of quantities 

added.

megagram (meg uh gram): A unit of mass 

equal to 1,000,000 grams. A megagram is equal 

to 1.1 ton, or 2,200 pounds. Symbol: Mg 

net (net): An amount, profit, weight, price, result, 

that is left after another amount is subtracted.

forest managers (för est mä ni jürz): Skilled 

individuals who takes care of natural resources.
39

The Natural Inquirer • Volume 9, Number 1

Thinking About 

Science

Scientists try to solve 

problems that are important 

to society. In some cases, 

scientists try to solve problems 

before they are even recognized 

as problems. In this study, for example, the 

scientists were aware that energy prices 

were continuing to rise. They reasoned that, 

at some point, it might become economically

possible to use tree crowns for wood energy 

in the Southeastern United States (figure 1). 

The scientists developed a study to better 

understand how much energy is available from 

tree crowns. As you can see, science is not 

just about solving today’s problems. Scientists 

also look into the future and anticipate future 

problems that may need to be solved.

Figure 1. A tree crown.

Thinking 

About the 

Environment

Trees are a valuable 

resource for the planet. They 

help to keep the air clean and 

hold soil in place. Trees absorb and hold carbon 

to reduce global climate change. They provide 

homes for animals and other plants. Trees are 

also renewable, meaning they can be planted, 

grown, and used for human needs. Some 

forests are planted and managed to eventually 

be used for wood products. Examples of 

wood products include furniture, lumber, and 

plywood.

When a forest is cut down to be used for 

wood products, only the tree’s trunk is used. 

Foresters call the tree’s trunk its bole. The rest 

of the tree, which is mostly the tree’s crown, is 

left behind. The crowns are usually piled and 

burned or left to decay (figure 2). In this way, 

the crown’s nutrients are returned to the soil to 

nourish the next generation of trees (figure 3).

Figure 2. Tree crowns piled together are called 

slash.

Figure 3. The movement of nutrients from trees 

to the soil. Most of the nutrients in a tree are 

stored in the crown. After a tree is cut or burned, 

the leafy crown and branch material is returned 

to the soil as it decays. The inorganic material 

comes from minerals.

Leaves fall

from the tree

"

Bacteria and fungi

consume the leaves

to get nutrients and

release inorganic

material into the soil

"

This inorganic

material provides

nutrients to

the tree

"
40

Bioenergy Edition, http://www.naturalinquirer.org

Introduction

Pine trees cover much of the Southeastern 

United States (figure 4). When older pine trees 

are cut for making wood products, only the 

trees’ boles are used (figure 5). The scientists 

in this study wondered if there might be a use 

for the trees’ crowns as well. In particular, they 

wondered whether the trees’ crowns might one 

day be a source of energy. A tree’s crown can 

be cut into small pieces and used in a woodburning furnace or converted to liquid fuels, 

such as ethanol. 

Based on the scientists’ research, they 

estimated an average hectare of southern pine 

forest contains 968 megawatt hours (MWh) of 

energy stored in its wood. Of this 968 MWh of 

energy, 112 MWh are stored in tree crowns and 

856 MWh of energy are stored in the boles. 

With over 36,000,000 hectares of southern 

pine forest, this amounts to a lot of stored 

energy.

After trees are cut, the crowns could be 

removed and burned to make energy. This 

also takes energy, however, as machines must 

be used to cut and haul the trees. Another 

thing to consider is that the crowns contain 

nutrients that should be returned to the soil. If 

the crowns are removed with the tree boles, 

the soil could become less healthy for the next 

generation of trees.

The scientists wanted to compare the 

amount of potential wood energy contained in 

southern pine tree crowns in three situations 

(figure 6). The first situation is when only 

the tree boles are removed from the area. 

The second situation is when entire trees are 

removed and tree crowns are used for energy. 

The third situation is a little more complicated. 

In this situation, whole trees are removed, the 

crowns are used for energy, and fertilizer is 

applied to the area to help new trees grow.

Figure 4. The Southeastern United States.

Figure 5. Only the boles of large southern pine 

trees are used for wood products.

Number Crunches

b	 OneMWh of energy is the amount of

electricity youwould use if you played

15,000CDs.Howmany CDs could be played

with the energy stored in 1 hectare of

southern pine forest? (Remember, a hectare

of southern pine forest contains 968MWh

of energy.)Howmany CDs could be played

with the energy stored in the crowns of

that1 hectare offorest? (One hectare oftree

crowns contains 112MWh of energy.)
41

The Natural Inquirer • Volume 9, Number 1

Table 1. Amount of energy in megawatt hours 

contained in a megagram (Mg) of forest 

biomass; and amount of energy needed to 

produce, package, transport, and apply 1 

kilogram (kg) of phosphorus and nitrogen 

fertilizer.

Amount of energy 

contained in a Mg of 

forest biomass

5.64 MWh

Amount of energy used 

to produce, package, 

transport, and apply 1 kg 

of nitrogen fertilizer

0.0021 MWh

Amount of energy used 

to produce, package, 

transport, and apply 1 kg 

of phosphorus fertilizer

0.022 MWh

The Situations The area is left 

with.... Soil preparation Tree planting

Wait 10 years 

to assess new 

amount of biomass

per hectare

Boles only 

removed

Tree crowns piled 

into slash

(see figure 2)

None (Some 

nutrients available 

through the slash) 

(see figure 3)

Yes Yes

Entire trees 

including crowns 

removed

Soil only No Yes Yes

Entire trees 

including crowns 

removed

Soil only Yes Yes Yes

Reflection Section

b	 Whatlarger social issue does this research

address? (Hint: it has to dowith somethingwe

use everyday forjust about everythingwe do.)

b Describe the questions the scientistswanted

to answer.

Method

The average amount of energy contained in 

a hectare of southern pine forest had already 

been calculated by other scientists. As well, 

the amount of energy used when fertilizer is 

produced, packaged, transported, and applied 

had been calculated earlier by other scientists 

(table 1). The scientists in this study were 

able to use this information without having to 

calculate it themselves. This is similar to what 

you do when you use information from the 

Internet, the library, or other source.

Figure 6. The three situations compared by the scientists.
42

Bioenergy Edition, http://www.naturalinquirer.org

The scientists identified an area of forest 

with 37-year-old southern pines on the 

Kisatchie (kuh sach e) National Forest in 

Louisiana (figure 6). The size of the area was 

0.6 hectares. First, they divided the area into 

three experimental plots. Each plot was the 

same size.

Figure 6. Locations of the Kisatchie National 

Forest in Louisiana.

The scientists calculated how much energy, 

measured in megawatt hours, is contained in 

the crowns of the three plots. They assumed 

each of the plots were equal in the amount of 

energy they contained.

The scientists then arranged to have the 

trees cut and removed (figure 7). In the first 

Number Crunches

b What was the size in hectares of each of 

the experimental plots? What was the 

size in acres? (One hectare is equal to 

2.47 acres.)

Figure 7. The scientists arranged to have the 

trees cut.

plot, only the boles were removed. The tree 

crowns were left on the ground. In the second 

two plots, entire trees, including the crowns, 

were removed. They applied fertilizer to the 

third plot. Then, they planted seedlings on all 

three plots so that a new generation of trees 

could grow (figures 8 and 9).

Figure 9. Over time a new generation of trees 

were allowed to grow.

Figure 8. Seedlings were planted on all three 

plots.
43

The Natural Inquirer • Volume 9, Number 1

The scientists calculated how much energy 

was used to acquire and apply nitrogen and 

phosphorus fertilizers to the third plot. Then, 

the scientists waited 10 years. At the end of the 

10 years, the scientists calculated how much 

energy might be available in the tree crowns 

growing on each of the three plots. They added 

the amount of energy available in crowns before 

the trees were cut with what they calculated 

was available in tree crowns after 10 years of 

growth.

Reflection Section

b The scientists used information that had 

been previously calculated by others. For 

the scientists’ research to be accurate, 

what do you think they needed to do 

and how should they feel about this 

information? In what ways do you or 

should you do the same thing when 

accessing information over the Internet? 

b What three things were the scientists 

comparing in this study?

Table 2. Amount of biomass and energy used in each of the plots. See key on page 44.

Experimental 

plots

Gain in energy 

in megawatt 

hours per hectare 

from the present 

cutting and use of 

tree crowns

Gain in energy 

in megawatt 

hours per hectare 

after 10 years of 

growth

Loss in energy in 

megawatt hours 

per hectare due 

to cutting trees 

and fertilizing 

after 10 years

Net amount of 

energy gain in 

megawatt hours 

per hectare after 

10 years

Removal of tree 

boles only

0

(Because the 

crowns were left 

on the ground 

and not used for 

energy)

0

(Because the 

crowns were left 

on the ground 

and not used for 

energy)

0

(Because the 

crowns were left 

on the ground 

and not used for 

energy)

0

(Because the 

crowns were left 

on the ground 

and not used for 

energy)

Removal of whole 

trees

115*

0

(Because no 

additional 

fertilizer was 

added to the soil.)

– 43**** 72

Removal of 

whole trees and 

fertilizing

115* 137** – 1.2***** 250.8

Findings 

The results of the experiment are shown in 

table 2.
44

Bioenergy Edition, http://www.naturalinquirer.org

The last column of table 2 is the most 

important. The scientists discovered that 

fertilizing the soil after cutting trees and 

removing the whole tree is a good way to 

ensure a higher energy potential in tree crowns 

after 10 years. Some scientists previously 

thought that the energy it takes to fertilize 

might not pay off in potential energy gains.

Key to Table 2

* Remember the scientists assumed that all plots started 

with the same amount of energy in their tree crowns that 

might one day be used.

** This number represents the gain in energy potential 

in the tree crowns after 10 years of growth. The gain is a 

result of adding fertilizer to the soil after cutting the trees 

and before planting new trees.

  This number represents a loss in energy potential.

This loss is caused because the trees did not grow as 

large as they could have. They did not grow as large 

because the crowns were removed from the site after the 

trees were cut. Remember that the crowns provide some 

nutrients to the soil that help trees grow.

** *** This number represents the loss of energy caused by 

having to package, transport, and apply the fertilizer.

Discussion

This study focused on southern pine forests. 

Forest managers believed that on southern 

soils, the energy used to apply fertilizer would 

be greater than future gain in energy from 

tree crowns. This research shows the gains in 

potential energy are greater than the energy 

used to fertilize soil before planting trees.

The scientists will do their calculations 

again when the trees are 25 years old. When 

the trees are 25 years old, the scientists will 

cut the trees and measure how much energy 

is contained in the tree crowns. They will do 

this for all three plots. At that time, they will 

again compare energy gain with energy used to 

fertilize the soil.

Reflection Section

b	 Look atthe last column oftable 2.Why do

you think the third plot shows amuch higher

energy potentialthan the second plot?

b	 In10years,tree crownsmightbe animportant

source of energy. Based on this research,what

one thingwould you recommend to someone

wanting to plant southern pine trees for

energy?

Reflection Section

b	 Imagine you are living 10years in the future.

Do you think energy fromtree crownswill be

more orless importantthan itis now?Why or

why not?

If you are a Project Learning 

Tree-trained educator, you 

may use Activity #15: “A Few 

of My Favorite Things,” or 

Activity #89: “Trees for Many 

Reasons”

From: Scott, D. A. and Dean, T. J. (2006). Energy 

trade-offs between intensive biomass utilization, site 

productivity loss, and ameliorative treatments in loblolly 

pine plantations. Biomass and Bioenergy 30, pp. 1001-

1010. http://www.srs.fs.usda.gov/pubs/ja/ja_scott007.pdf
45

The Natural Inquirer • Volume 9, Number 1

FACTivity

Time Needed

1 class period 

Materials

Blank sheets of white paper (one for each 

student), markers, and photos of different 

tree stands (on page 46).

Note: In advance, your teacher may want 

to examine the trees in the schoolyard to 

identify potential trees for this activity.

The questions you will answer with this 

activity are:

1. Why are trees managed differently?

2. What are some of the differences in 

managed trees versus unmanaged 

trees?

Before you begin, recall that trees are a 

valuable resource for the planet. They help 

to keep the air clean and hold soil in place.

Trees absorb and hold carbon to reduce 

global climate change and provide homes 

for animals and other plants.

Trees are also renewable, meaning 

they can be planted, grown, and used for 

human needs. Some forests are planted 

and managed to eventually be used for 

wood products. Examples of wood products 

include furniture, lumber, and plywood. Any 

tree could be a source of biofuel, but some 

trees are better for different needs. Trees 

in managed areas—plantations, around 

houses, buildings, or schoolyards—can be 

groomed to create different forms. A tree 

farm manager may cut off limbs of trees to 

make them grow straighter and have fewer 

limbs. Some tree managers want the tree to 

have a wide low crown, so the tree will be 

cut on the top to grow out.

These different forms provide different 

uses as mentioned before. Straighter 

growing trees and trees with fewer limbs 

on the trunk may be better for lumber or 

pole products. Trees with many limbs may 

be used by wildlife for protection. Larger 

crowns provide a shady place for people 

and wildlife. Can you think of other forms of 

trees with different uses? Remember not all 

trees should be managed by people. Think of 

natural forests. How do trees grow and look 

in those areas?

Now, as a class:

With other classmates, brainstorm about 

how trees are managed in different ways 

other than for wood products. How are these 

trees similar or different from trees used for 

lumber? For example, ornamental trees in a 

schoolyard or around a home may not have 

a straight form, like pine trees grown for 

lumber. However, trees around the school 

and house need to be pruned and de-limbed 

so not to damage the house or school. Other 

trees are managed to provide food, such 

as fruits and nuts. See how many different 

things you can identify for which trees are 

managed.

Activity

1. Go outside. Select a tree and draw the 

tree’s form on your sheet of paper. Focus 

on limb, crown, and trunk form.

2. If time allows, draw a second tree 

(preferably a different form) to have a 

comparison.

3. Inside: Examine the photos on the next 

page of differently managed trees and 

compare them with the trees you have 

drawn.

4. Think about the managed trees in the 

photos and their uses compared to the 

trees you drew. Can you guess how your 

drawn tree might be used and who might 

use it? Don’t forget uses of the tree by 

wildlife, including mammals, insects, birds, 

reptiles, and amphibians.
46

Bioenergy Edition, http://www.naturalinquirer.org

Additional information for the classroom

The title of this article, “How Now Round Crown?” is a take-off on the phrase, “How Now 

Brown Cow?” This phrase is nonsensical, having no real meaning, but has sometimes been used 

as a jovial greeting. The phrase was once used to teach rounded vowel sounds for proper public 

speaking. (From http://www.phrases.org.uk/)

Courtesy of Barbara McDonald, Forest Service

Courtesy of Barbara McDonald, Forest Service

Courtesy of Barbara McDonald, Forest Service

Courtesy of Barbara McDonald, Forest Service

Courtesy of Stephen Fraedrich, Forest Service

Courtesy of Barbara McDonald, Forest Service

Courtesy of Howard Schwartz,

Colorado State University,

http://www.bugwood.org
47

The Natural Inquirer • Volume 9, Number 1

As teachers of science, you want your 

students to acquire abilities that will 

enable them to conduct scientific inquiry, 

and you want them to gain an understanding 

of the scientific inquiry process. Scientific 

inquiry can best be taught by integrating 

minds-on and hands-on experiences. Over 

time, such experiences encourage students 

to independently formulate and seek answers 

to questions about the world we live in. As 

educators, you are constantly faced with 

engaging your students in scientific inquiry in 

new and different ways. In an age of abundant 

technology, standard teaching strategies can 

become monotonous to today’s learners. The 

Natural Inquirer provides a fresh approach to 

science and a view of the outside world that is 

larger than the classroom and can still be used 

while in the school setting.

The Natural Inquirer is a science education 

resource journal to be used with learners from 

Grade 5 and up. The Natural Inquirer is written 

at the 7th grade level, but students from grade 

5 upward have found the articles useful. The 

Natural Inquirer contains articles describing 

environmental and natural resource research 

conducted by the Forest Service scientists and 

their research cooperators. These are scientific 

journal articles that have been reformatted to 

meet the needs of middle school students. The 

articles are easy to understand, aesthetically 

pleasing to the eye, contain glossaries, and 

include hands-on activities. The goal of the 

Natural Inquirer is to stimulate critical reading 

and thinking about scientific inquiry and 

investigation while learning about ecology, the 

natural environment, and natural resources.

The Format of a

Natural Inquirer 

Article

Each Natural Inquirer article follows the same 

format. Natural Inquirer articles are written 

directly from a published science article. All 

rewritten articles have been reviewed by the 

scientists for accuracy. Each article contains the 

following sections, which you may introduce to 

your students as they read:

Meet the scientists: Introduces students to 

the scientists who did the research. Can be 

used in a discussion of careers in science.

Glossary: Introduces possibly new scientific 

or other terms to students. The first 

occurrence of a glossary word is italicized in 

the text.

Thinking About Science: Introduces 

something new about the scientific 

process, such as a scientific habit of mind or 

procedures used in scientific studies.

Thinking About the Environment:

Introduces the environmental topic being 

addressed in the research.

Introduction: Introduces the problem or 

question being addressed by the research.

Method: Describes the method used by the 

scientists to collect and analyze their data.

Findings: Describes the results of the analysis.

Discussion: Discusses the findings and places 

them into the context of the original problem 

or question. 

Reflection Section: Questions to promote 

critical thinking about science.

Citation: Gives the original article citation, 

and a Web site address to access the original 

scientific article. 

FACTivity: A hands-on activity that reinforces 

an aspect of the research.

Note to Educators
48

Bioenergy Edition, http://www.naturalinquirer.org

Science Education 

Standards

and Evaluations

In the back of the journal, you will find a 

list that allows you to identify articles by the 

national science education standards they 

address. You and your students may also 

complete evaluation forms online by visiting 

http://www.naturalinquirer.org.

If you have any questions or comments, 

please contact:

Dr. Barbara McDonald

Forest Service

320 Green St.

Athens, GA 30602-2044

706.559.4224

bmcdonald@fs.fed.us

(Please put “Educator Feedback”

in the subject line)

Educator Resources

Visit the Natural Inquirer Web site at

http://www.naturalinquirer.org. From this site, 

you can read and download lesson plans, word 

games, and other resources to help you use 

the Natural Inquirer in your classroom. You can 

also view and download a year-long lesson plan 

aimed at helping your students learn about the 

scientific process.
49

The Natural Inquirer • Volume 9, Number 1

Lesson Plan

Procedures

In advance:

Make a copy of the 42 questions on page 

51 and cut them into strips (one strip for each 

question). Fold the strips in half and put them 

into a box or hat. 

In class (3 minutes):

Have students write the following headings 

on their lined paper. Students should leave three 

blank spaces in between each heading.

•	 Meet the Scientists

•	 Science

•	 Environment

•	 Introduction

•	 Methods

•	 Findings

•	 Discussion

Pass the box or hat around the room and 

have each student pull out one strip of paper. 

30 minutes:

Read each of the seven sections of the 

Natural Inquirer article aloud in class. Ask for 

student volunteers to read one paragraph each. 

Skip the “Reflection Sections” and “Number 

Crunches,” but examine any illustrations, 

charts, or graphs. At the conclusion of each 

section, students should complete the question 

they have pulled, based on information in the 

section. They should write their question in the 

This is a generic lesson plan that can be 

used with any Natural Inquirer article, 

including all of the articles in this journal. You 

may also visit http://www.naturalinquirer.

org and view or download “FACE Look!” or 

“Worming Their Way In” for more generic 

lesson plans, which are located at the back of 

each monograph. 

This lesson plan is an adaptation of the 

“Questions Only” Reading Strategy. The goal 

is to help students identify key concepts and 

develop their own interpretations of what 

they read. This is especially important as a 

foundation for developing critical thinking skills 

in science.

This lesson plan is based on a typology of 

thinking called Bloom’s Taxonomy, developed 

in 1956. It identifies six categories of thinking: 

Knowledge, Comprehension, Application, 

Analysis, Synthesis, and Evaluation. For more 

information, search the Web for Bloom’s 

Taxonomy.

Time Required

1 class period (2 class periods with optional 

“hands-on” activity)

Materials

Natural Inquirer article, question strips (see 

p. 51), one sheet of lined paper and pencil per 

student
50

Bioenergy Edition, http://www.naturalinquirer.org

correct section of their lined paper. Be sure to 

give students a few moments to formulate their 

question, and encourage them to reflect on the 

section before writing their question.

Now, have students pass their question (on 

the paper strip) to the student next to them. 

Repeat the process with each section. At the 

end, students should have formulated a different 

question for each of the seven sections. 

5 minutes:

Quickly review the article by holding a class 

discussion using the following questions:

1. What was the problem the scientists wanted 

to address? (From the “Introduction” 

Section)

2. What was the question the scientists wanted 

to answer? (From the “Introduction” 

Section)

3. What did the scientists do to answer the 

question? (From the “Methods” Section)

4. What did the scientists discover? (From the 

“Findings” Section)

5. What was the key point of the “Discussion” 

section?

10 minutes:

Now, review each article section by having 

students share their questions. See if anyone in 

the class can come up with an answer to the 

questions. Encourage students to use logic to 

develop answers. In some cases, answers will 

be pure speculation. This is okay. The exercise 

is intended to have students identify questions 

that will help them think about their reading, 

and to consider potential answers to these 

questions.

Remind students that as they read, they 

should always be asking questions about 

the content. When they read science, they 

should ask critical questions, such as questions 

beginning with who, what, when, where, why, 

and how. 

Optional (2nd day)

1 class period:

Quickly review the article from the previous 

day. Do the FACTivity associated with the 

article. The FACTivity can be found at the end 

of each article.
51

The Natural Inquirer • Volume 9, Number 1

Who......

What.....

Where else.....

What if......

When will.....

How.....

What would happen if.....

How would you test.....

How would you apply.....

What does.....

How would you compare.....

Do you think.....

Why did....

What else.....

How did.....

How would you change.....

How is ____ like......

Who else.....

What is.....

What did.....

Where.....

Why do.....

When did.....

When would.....

Why was it better to.....

Can you connect ___ with....

Where have I heard about....

Do you think.....

Why.....

What is one.....

How could.....

Where did.....

What is the most.....

Could.....

How could.....

Who was.....

How could you explain.....

What is most important.....

What difference....

Which do you.....

What do you think.....

What evidence.....
52

Bioenergy Edition, http://www.naturalinquirer.org

Reflection Section Answer Guide

Chip Off The Old Block

Introduction

• What is the question the scientists 

wanted to answer? Would school districts 

save money if they used wood for heating 

instead of their usual way of heating schools 

using fossil fuels?

• What would the scientists have to do to 

answer their question? Although students 

may come up with many ideas, they should 

identify at least three things: Current heating 

costs at the schools must be understood, a new 

wood burning heating system would have to be 

built at the schools, and costs of the new system 

must be tracked.

Method

• Should the scientists include the 

following costs in their calculations: 

The cost of cutting trees, the cost of 

transporting cut trees to a mill for 

cutting into chips, and the cost of 

transporting the wood chips to the 

school? Why or why not? Yes, since these 

are real costs associated with biomass heating, 

they should be included in the scientists’ 

calculations.

• Biomass heat, which comes from 

wood chips, is considered a renewable 

natural resource because trees can 

be replanted. What is one advantage 

of using biomass energy over a 

nonrenewable resource such as oil? 

What is one disadvantage? Renewable 

resources can be sustainable into the future, 

since trees and other biomass energy products 

can be replanted. In this case, the trees were 

being cut anyway, and this provides a way 

to use them for human benefit. A possible 

disadvantage is if too many trees are cut for 

biomass heat energy, there will be fewer trees to 

provide benefits such as carbon sequestration, 

wildlife habitat, and protection from soil 

erosion. 

Findings

• Look at table 1. You can see the cost of 

oil had risen between 2003 and 2005, 

and, therefore, the cost savings rose 

over the 2 years. Based on what you 

know about oil prices now, do you think 

the cost savings for Darby Schools went 

up, down, or stayed the same during the 

last school year as compared with 2004–

2005? Fuel prices have been rising annually, 

therefore, students should conclude that the 

cost savings associated with using biomass heat 

energy should be steadily climbing. The answer 

to this question, however, will depend on 

whether fuel prices are currently higher or lower 

than prices in 2004–2005.

• Do you think the cost savings would be 

the same for a school located in Kansas 

as in Montana? Why or why not? You 

may have to help your students think this 

through. There are not as many forests nearby 

in Kansas as there are in Montana. Therefore, 

wood chips would have to be transported to the 

school, raising the cost of biomass heating for 

Kansas’ schools. While it is unknown whether 

there would be cost savings, it is clear that any 

costs savings would have to be less in Kansas 

than Montana. 

Discussion

• Should the cost of replacing a 

conventional heating system with a new 

biomass system be considered when 
53

The Natural Inquirer • Volume 9, Number 1

calculating cost savings? Why or why 

not? Yes, because these costs are real.

• Should the cost of building a new 

biomass heating system at a new 

school be considered when calculating 

cost savings? Why or why not? Not 

necessarily. If total cost savings are to be 

calculated, one could compare the cost of 

building a conventional oil heating system with 

the cost of building a biomass system. Then, 

the operational costs could also be compared. 

Otherwise, it is probably okay just to compare 

estimated costs of heating with oil with actual 

costs of heating with biomass energy.

Which Do You A-door?

Introduction

• In your own words, state the question 

the scientists wanted to answer. Does the 

process up to and including the manufacture 

of a wood door strengthened with fiberglass or 

a steel door use more energy and create more 

waste?

• Where do people get the raw materials 

they need to manufacture products? 

From natural resources that came from Earth. 

Method

• The scientists included the energy used 

and emissions produced when the raw 

materials were collected, as well as the 

manufacture of each door. Why do you 

think they included the gathering of raw 

materials in the life-cycle inventory?

If the scientists wanted to compare the total 

amount of energy used and emissions produced 

in the manufacture of each door, they would 

have to include the energy used and emissions 

produced to harvest or mine the raw materials 

and transport them to a manufacturing plant.

• Do you think the scientists found it 

takes more energy to manufacture 

a wood door or a steel door? Why?

Students will have to use their own critical 

thinking skills to determine which door they 

think is more environmentally sound in the 

manufacturing process. Whatever students 

report, they should support their conclusion 

with logically derived reasons.

Findings

• Examine tables 1–5. What conclusion 

can you make about the production 

of a steel door in comparison with the 

production of a wood door? Students 

should see that more energy is used and waste 

products produced in the manufacture of a steel 

door as compared with a wood door.

• Based on the findings you have just 

read, what would you predict about the 

environmental impact of manufacturing 

a steel table compared with 

manufacturing a wood table? Students 

should predict that the manufacture of a steel 

table would take more energy and produce 

more waste products than the manufacture of a 

wood table.

Discussion

• This life-cycle inventory showed 

that more energy is used and more 

waste produced in the manufacture 

of a steel door. What might be one 

advantage of using a steel door instead 

of a wood door in your home? Do you 

think this advantage of using a steel 

door outweighs the disadvantage of its 

greater environmental impact? Why or 

why not? One advantage of using a steel door 

might be its greater resistance to burglary. With 

added fiberglass, however, wood doors are 

made much stronger. Hold a class discussion 

about the relative importance of the advantages 

and disadvantages of steel and wood doors.

• If you were employed by a home 

improvement store in your community, 

what would you tell a homeowner who 
54

Bioenergy Edition, http://www.naturalinquirer.org

has come into your store wanting to buy 

a new door for his or her home? Students 

will have to answer this question on their 

own. They should, however, be able to restate 

the findings of this research and integrate 

information from the class discussion held as a 

part of the reflection question above.

Chip and Truck

Introduction

• What question did the scientists want 

to answer? What are the costs, revenues, and 

benefits of using woodchips for thermal energy, 

and how does using woodchips compare with 

burning small trees on the forest?

• What are the sources of the two types 

of fuel being compared in this study? 

Which of these fuels is renewable? Diesel 

fuel to cut and haul the woodchips comes from 

oil; and thermal energy comes from woodchips 

cut from small trees. The woodchips are 

renewable because new trees can be grown.

Method

• Whenever people make a choice to 

do one thing rather than something 

else, there are costs and benefits to 

each choice. Think about a choice you 

recently made. Identify the costs and 

benefits of that choice, compared with 

another choice you could have made 

instead. Remember that costs involve 

more than just money. For example, 

time, or even the loss of a friendship, 

can be considered a cost. This is an 

individual question, and each student will have 

to answer for him or herself. The important 

point here is to emphasize how people analyze 

(or should analyze) costs and benefits before 

making a decision. You may want to use the 

example of risky behavior as something to be 

carefully analyzed before a decision is made.

• In this study, there is one cost in 

particular that continues to rise. What 

is that cost? How do you think this cost 

might affect the scientists’ results if 

they did this study next year? Fuel costs 

continue to rise. Students should be encouraged 

to think beyond the costs of cutting trees and 

woodchips and hauling them. They should also 

consider the rising costs of conventional heating 

and how heating with thermal energy from 

woodchips may offset some of the rising fuel 

costs.

Findings

• Look at figure 6. Where does most of 

the revenue come from in this situation? 

Most of the revenue comes from selling the 

larger trees to a mill.

• It makes sense to cut trees into 

woodchips when facilities that can 

use woodchips are located close 

by. However, few of these facilities 

currently exist. As fuel costs rise, in 

what ways might this situation change? 

This is a good group or class discussion 

question. Students should realize that as fuel 

costs rise, hauling costs will rise. Heating oil 

costs will also rise, making woodchips more 

attractive. Some possibilities are that more 

woodchip facilities will be built in areas close to 

forests, making it more economically feasible. If 

hauling costs continue to rise and more facilities 

are not built close to forests, it may remain 

difficult to make woodchip heating feasible. 

Students should be encouraged to consider 

a number of options for the future in which 

woodchips might be a good option for some 

kinds of energy.

Discussion

• The scientists pointed out a dilemma 

that could be faced in the future. 

What is that dilemma? To make the use 

of woodchips for energy more economically 
55

The Natural Inquirer • Volume 9, Number 1

feasible, more woodchip facilities need to 

be built near forested areas. As more small 

trees are cut and the forest regains its health, 

fewer small trees will be available to fuel the 

woodchip facilities. Thus, it is possible that, in 

the future, there will be a shrinking supply of 

small trees to cut into woodchips and use in the 

facilities. 

How Now Round 

Crown?

Introduction

• What larger social issue does this 

research address? (Hint: it has to do 

with something we use everyday for just 

about everything we do.) This research 

addresses the energy issue. How does it address 

this issue? This research attempts to provide 

information about whether it is reasonable to 

use southern pine tree crowns as an energy 

resource.

• Describe the questions the scientists 

wanted to answer. This is a question that 

should help clarify whether students understand 

the research questions. Students should 

understand that the scientists were exploring 

how tree crowns might be used for energy and 

the effect of different ground treatments on 

future energy availability. 

Method

• The scientists used information that 

had been previously calculated by 

others. For the scientists’ research to 

be accurate, what do you think they 

needed to do and how they should feel 

about this information? The scientists 

would need to check the accuracy of the 

information they were about to use. They 

must feel confident the information they were 

using was accurate. When you have not 

calculated the information yourself, you must 

be as certain as possible that it is accurate. In 

what ways do you or should you do the 

same thing when accessing information 

over the Internet? One should not consider 

information factual just because it was found 

on the Internet. Multiple sources should be 

compared and contrasted. Sites with extensions 

of .gov and .edu should be used if possible. 

These are governmental and educational 

institution sites.

• What three things were the scientists 

comparing in this study? The amount of 

extra energy available for use in 10-year old 

trees growing in three different situations. In 

the first situation, the tree crowns would not 

be available for use. In the second, the crowns 

would be available, but the ground had not 

been fertilized before planting. In the third, the 

crowns would be available and the ground had 

been fertilized before planting. 

Findings

• Look at the last column. Why do you 

think the third plot shows a much 

higher energy potential than the second 

plot? Because the fertilization helped the trees 

to grow larger and, therefore, provide more 

biomass that can be used to create energy.

• In 10 years, tree crowns might be an 

important source of energy. Based on 

this research, what one thing would 

you recommend to someone wanting to 

plant southern pine trees for energy? 

Fertilizing the ground is important if you want 

to grow larger and healthier trees.

Discussion

• Imagine you are living 10 years in the 

future. Do you think energy from tree 

crowns will be more or less important 

than it is now? Why or why not? Students 

may have a variety of opinions about this. 

Whatever they say, they should have logical 

reasons for their position.
56

Bioenergy Edition, http://www.naturalinquirer.org

Which National Science Education Standards 

Can Be Addressed by This Natural Inquirer? Which Do You A-door? A Chip Off the Old Block How Now Round Crown? Chip and Truck

National Research Council, Content Standards, Grades 5-8.

Science as Inquiry

 Abilities Necessary To Do Scientific Inquiry x x x x

 Understanding About Scientific Inquiry x x x x

Life Science

 Regulation & Behavior x x x

 Populations & Ecosystems x x

 Diversity & Adaptations of Organisms x x

Science & Technology

 Understanding About Science & Technology x x x x

Science in Personal & Social Perspectives

 Risks & Benefits x x x x

 Science & Technology in Society x x x x

History & Nature of Science

 Science as a Human Endeavor x x x x

 Nature of Science x x x x

56

Bioenergy Edition, http://www.naturalinquirer.org
What Is the USDA 

Forest Service?

The Forest Service is a part of the 

United States Department of Agriculture 

(USDA). It is made up of thousands of 

employees who care for the Nation’s forest 

land. The Forest Service manages more 

than 150 national forests and almost 20 

national grasslands. These are large areas 

of trees, streams, and grasslands. National 

forests are similar in some ways to national 

parks. Both are public lands, meaning 

that they are owned by the public and 

managed for the public’s use and benefit. 

Both national forests and national parks 

provide clean water, homes for the animals 

that live in the wild, and places for people 

to do fun things in the outdoors. National 

forests also provide resources for people to 

use, such as trees for lumber, minerals, and 

plants used for medicines. Some people in 

the Forest Service are scientists, whose 

work is presented in the journal. Forest 

Service scientists work to solve problems 

and provide new information about natural 

resources so that we can make sure our 

natural environment is healthy, now and into 

the future.

What Is the 

Cradle of 

Forestry 

Interpretive 

Association?

The Cradle of Forestry in America 

Interpretive Association (CFIA), a 501c3 

nonprofit organization, was founded in 

1972 by a group of conservationists to help 

the Forest Service tell the story of forest 

conservation in America and to help people 

better understand both forests and the 

benefits of forest management.

USDA Forest Service

http://www.fs.fed.us

The Natural Inquirer

http://www.naturalinquirer.org

Conservation Education

http://fs.usda.gov/conservationeducation

Cooperative State Research, Education, and 

Extension Service 

http://www.csrees.usda.gov

Agriculture in the Classroom

http://www.agclassroom.org

NatureWatch

http://www.fs.fed.us/outdoors/naturewatch/

Smokey Bear

http://www.smokeybear.com

Project Learning Tree

http://www.plt.org/

National Forests by Map

http://www.fs.fed.us/recreation/map/finder.shtml

National Forests by State

http://www.fs.fed.us/recreation/map/state_list.shtml

Visit These Web Sites for More Information
Natural Inquirer editorial review board members: Clarke Middle School, Clarke County, Georgia

FS-927

Spring 2009

United States 

Department 

of Agriculture

Forest Service

Natural Inquirer

http://www.naturalinquirer.org

Forest Service

http://www.fs.fed.us

Forest Service Conservation Education

http://www.fs.usda.gov/conservationeducation

Kids.gov—Earth science for middle school

http://www.kids.gov/6_8/

6_8_science_environment.shtml

Visit These Web Sites for More Information About Bioenergy

The U.S. Department of Agriculture (USDA) prohibits discrimination in 

all its programs and activities on the basis of race, color, national origin, 

age, disability, and where applicable, sex, marital status, familial status, 

parental status, religion, sexual orientation, genetic information, political 

beliefs, reprisal, or because all or part of an individual’s income is derived 

from any public assistance program. (Not all prohibited bases apply to 

all programs.) Persons with disabilities who require alternative means for 

communication of program information (Braille, large print, audiotape, 

etc.) should contact USDA’s TARGET Center at (202) 720–2600 (voice 

and TDD). To file a complaint of discrimination, write to USDA, Director, 

Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C.

20250–9410, or call (800) 795–3272 (voice) or (202) 720–6382 (TDD). 

USDA is an equal opportunity provider and employer.

Energy Kids Page

(Energy Information Administration)

http://www.eia.doe.gov/kids/energyfacts/sources/

renewable/biomass.html

National Renewable Energy Laboratory

http://www.nrel.gov/learning/

Fuels for Schools

http://www.fuelsforschools.info/